This application claims the priority of German Patent Application Serial No. 199 20 466.7, filed May 4, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates especially but not exclusively to a method for cleaning an interior space of a coating booth, in particular a powder coating booth, as well as to a novel design of a cleaning device for such coating booth.
WO 96/12568 discloses a powder coating booth with an interior space which is bounded by a preferably jacket-like peripheral wall, a floor and a ceiling. This coating booth includes a cleaning device which is capable of cleaning the interior space of the powder coating booth by moving in a vertical direction. During the coating operation, this cleaning device is kept ready for use outside the coating booth and can be introduced in a suitable manner into the interior space of the coating booth to clean the interior space of the powder coating booth, and can then clean the entire powder coating booth by moving in a vertical direction. The cleaning device, when not in use, requires storage space near the powder coating booth which adversely affects the compactness of the design of the powder coating booth.
It would therefore be desirable and advantageous to provide an improved method for cleaning an interior space of a coating booth, in particular a powder coating booth, as well as a coating booth, in particular a powder coating booth, to obviate prior art shortcomings and of a configuration which is compact and yet is reliable in operation to clean the effectively and essentially automatically.
According to one aspect of the invention, a method is provided for cleaning an interior space of the coating booth, in particular a powder coating booth, with an air-supported cleaning device and optionally a recovery device as well as a suction device extending in a longitudinal direction of the booth. The method provides that, if powders of an identical or similar color are employed, then blast air is blown against the surfaces of the interior space of the booth to be cleaned and thereafter directed towards a recovery device. Such cleaning method is particularly suited for a coating operation with a color change xe2x80x9ctint-in-tintxe2x80x9d, since in this case, due to the small difference in tint of the color powder, the excess powder needs to be cleaned off from the interior space of the booth only coarsely before being transported to the recovery device for reuse. To discharge the excess powder to the recovery unit, a conventional slotted suction device can be used. The conventional device is typically intended to operate only briefly in the coating booth and preferably extends in the longitudinal direction of the booth.
According to a different embodiment of the method for cleaning the interior space of the coating booth, in particular a powder coating booth, with an air-supported cleaning device, optionally also with a recovery device as well as a suction device extending in the longitudinal direction of the booth, blast air is blown against the surfaces of the interior space of the booth to be cleaned for a primary cleaning, for example during a color change, and again suctioned off, and optionally transferred to the recovery device or to a secondary filter. With such an embodiment of the method, steps are carried out simultaneously or alternatingly, wherein blast air is directed to the surfaces of the interior space of the booth to be cleaned and optionally suctioned off with a corresponding additional suction device, which can be provided in addition to the suction device that extends in the longitudinal direction of the booth. The blast air herein blows the powder particles off the corresponding wall surface of the interior space, and the released powder particles are then withdrawn from the interior space of the booth by suction as closely as possible to the release location. By combining the blowing and suction operation, the cleaning process is extremely effective and complete.
According to a preferred embodiment of the method, blast air with a certain pressure is first blown against the surfaces of the interior space of the booth to be cleaned, and the powder particles released by the blast air are subsequently suctioned off while the supply of blast air to the interior space of the booth is stopped. It will be understood that the order of the operation can also be reversed. Moreover, cleaning by alternatingly blowing and suctioning can also be carried out several times. The corresponding processes can be suitably adapted to a particular application.
According to an alternative embodiment of the method, blast air is blown against the surfaces of the interior space of the booth to be cleaned and simultaneously suctioned off, preferably at a different location from the blast air. According to a modification of the cleaning method of the invention, the blast air can be supplied and suctioned off simultaneously.
In all the aforedescribed cleaning methods of the invention, the blowing and/or suction operation can be performed cyclically, optionally several times. The process for a respective cycle is herein selected from previously obtained empirical values and by taking into account the economical impact of the cleaning method.
According to another embodiment, blast air is introduced intermittently or pulse-wise, in order to enhance the release of powder particles from the corresponding surface to be cleaned.
In particular, the blast air can be supplied under a controllable high pressure. In this way, the blast air only needs to be directed during a relatively short time to the respective surfaces of the interior space of the booth to be cleaned. This reduces the time required for carrying out the cleaning method of the invention, thereby significantly reducing the necessary downtime of the booth for cleaning.
Preferably, the cleaning method of the invention also provides that the supply of blast air is discontinued during the coating operation and that the air is withdrawn from the interior space of the booth through the floor and/or a side outlet extending in the longitudinal direction of the booth.
According to another aspect of the invention, a coating booth, in particular a powder coating booth, is provided which has a peripheral wall, a floor and a ceiling that cooperatively bound an interior space. The interior space can be cleaned with a cleaning device moving in a vertical direction. The floor and/or the ceiling of the coating booth are in the form of segments that are separate from the peripheral wall and also include the cleaning device.
The floor and/or the ceiling therefore also support the cleaning device. Alternatively, the cleaning device can be integrated in the floor section and/or the ceiling section. The coating booth of the invention does not require additional storage space for a cleaning device, since the floor section and/or the ceiling section themselves perform the cleaning by moving in a vertical direction. Accordingly, such coating booth can have very compact design and be advantageously employed when installation height and space are limited. Moreover, the appropriate facilities for the cleaning device as well as the appropriate drive units for moving the cleaning device to perform cleaning tasks can also be installed at suitable locations in the powder coating booth. Depending on the height of the booth or other limitations, it may be sufficient to employ for cleaning only the floor section or the ceiling section of the cleaning device; however, but it would also be possible to simultaneously or alternatingly use both the ceiling section and the floor section for cleaning. If both the floor section and the ceiling section are provided with a cleaning device, then one of the cleaning devices could be used for blowing and/or suction, while the other cleaning device could be designed as a fine cleaning device, to be used, for example, for wiping with a sponge or the like. Of course, optionally one of the cleaning devices can also be implemented as a pre-cleaning device.
For cleaning the interior space of the coating booth, the floor section and/or the ceiling section are moveable in a vertical direction, so that the entire interior space is attended to by the cleaning device and then cleaned. If both the floor section and the ceiling section are equipped with a cleaning device, then the distance traveled by these sections in the vertical direction can be reduced during cleaning, so that the cleaning operation can be performed faster, permitting a color change in an economical and effective fashion with less downtime.
Preferably, each cleaning device includes a blowing device and a suction device. The blowing device and suction device are preferably spaced apart from one another in an axial direction. Advantageously, the suction device and the blowing device are close to one another, so that the powder particles released from the interior wall by the blowing device reach the suction device on the shortest possible path, and the particles then reach the filter and cyclone device and optionally also the recovery device connected after the suction device. The blowing device can be used to direct an air jet onto the appropriate wall regions of the powder coating booth so as to support a complete release of the powder adhering to the wall surfaces and to move the released powder to the suction device.
The forward region of the cleaning device, as viewed in the movement direction, can be implemented as the blowing device, and the trailing region as the suction device. This arrangement can also be reversed. It is important that the blowing device and the suction device are arranged as closely as possible, so that the powder released from the wall surfaces travels the shortest possible path to the suction device.
Suitably, the blowing device and the suction device associated with the floor section may be formed as a nozzle plate, with the suction on the corresponding peripheral wall section occurring in the immediate vicinity of the impact region of the blast air. With this arrangement, the corresponding peripheral regions of the interior space of the booth can be cleaned effectively by preventing the powder that has been removed from the surface by the blast air to re-enter those areas of the booth that have already been cleaned. In addition, the cleaning device associated with the floor section can have a compact design, in particular a small height.
Suitably, the blowing device may include several nozzles which are distributed along the periphery and direct the blast air against the wall surface of the booth to be cleaned. The blowing device preferably also includes several suction openings which are also distributed along the periphery. The powder released from the wall surface of the booth by the blast air can reach the suction openings on the suction device via the shortest possible path. In another words, the cleaning device can clean the interior space of the booth completely and efficiently within a very short time. This ensures a very economical operation when coating articles, in particular in continuous operation.
Advantageously, in addition to the floor section and/or ceiling section, a sealing element can be provided which provides a reliable seal during the coating operation and also prevents powder particles from being released into the environment when the floor section and/or the ceiling section move vertically during the cleaning operation.
The bottom section and/or the ceiling section may includes several segments which can be moved relative to one another. In such an embodiment, the segments of the floor section and/or the ceiling section can be moved towards one another, thereby reducing their outside dimensions. In this arrangement, the sections can clean the inside of the booth in the vertical direction as intended. More particularly, the segments of the ceiling section of those booths that have in their ceiling section a through-slot for passage of a suspension gear of a conveyor, can be reliably sealed during the coating operation by their own weight and by making contact with the associated boundary of the peripheral wall. These segments are moved towards each other during cleaning and hereby assume dimensions that make it possible for them to move in the interior space of the coating booth in the vertical direction, thereby permitting the cleaning operation to take place.
In an advantageous embodiment of the coating booth of the invention, the blowing device associated with the ceiling section has the form of a blowing ring adapted to the cross-section of the coating booth, wherein the blowing ring can be arranged to face the interior space when the segments of the ceiling section are closely spaced.
The blowing device can have nozzles with corresponding nozzle exit openings arranged in the circumferential direction, which are constructed in such a way that blast air can be used to simultaneously, reliably and quickly clean the ceiling section and optionally the floor section.
In one embodiment wherein only the floor section is moveable in the interior space of the cabin, an actuating device which moves the segments of the ceiling section towards one another for cleaning and optionally lifts the segments slightly away from the upper edge of the peripheral wall, can be associated with a ceiling section of the aforedescribed embodiments. Advantageously, the actuating device can be implemented in form of an articulated lever mechanism. An actuating device of this type can be used to move the two segments of the ceiling section, on one hand, into a cleaning position and, on the other hand, into an operating position for performing a conventional coating operation. It will be understood is that corresponding suction devices can be associated with the ceiling segments.
Additional conventional seals can optionally be provided in the regions between the moveable ceiling sections and/or floor sections to ensure that in a typical coating operation, the interior space of the booth is reliably sealed by the ceiling section and/or the floor section.
In particular, if the ceiling section includes two segments, then separate blowing and suction devices can be associated with each segment. However, the segments can also be constructed so that in a closely spaced position, the device for blowing and the device for suction are both associated with the two segments. The corresponding supply and discharge lines are then provided eccentrically only on one segment of the ceiling and/or floor section.
The corresponding hose and pipe connections to the cleaning device are, of course, constructed so that they can follow the movement of the floor section and/or the ceiling section without impediment. For example, tubular sections that move inside one another in a telescopic fashion can be used for the suction device or the like, and the hose connection that supplies, for example, blast air can initially be wound up on a hose reel and is withdrawn from the hose reel during the vertical movement for cleaning. This design prevents the back and forth vertical movement of the supply lines from obstructing the cleaning operation.
Suitably, controllable flaps adapted for connection to subsequent cyclone devices, secondary filters device and/or recovery devices may be provided in a region of the suction devices. During cleaning, in particular during a color change xe2x80x9ctint-in-tintxe2x80x9d, the suction device associated with the floor section and/or ceiling section can be decoupled by placing the flap of the flap arrangement in a closed position. In this way, the suction device which extends predominantly in the longitudinal direction of the booth and is typically present in the interior space of the cabin during the coating operation, can be used to return to the removed powder directly to the recovery device. It will be understood that additional flaps can be arranged in the region of the suction device to suitably divert the removed powder.
In addition, the invention provides a coating booth of the aforedescribed type, which according to an alternative embodiment is constructed so that at least one ceiling cleaning device is associated with the ceiling section, with the ceiling cleaning device including compressed air nozzles for blowing off the adhering powder and at least one suction device disposed in the ceiling cleaning device for the blown-off powder, wherein the ceiling cleaning device in its end position cleans the entire space between the ceiling section and the floor section. With this arrangement, a self-sufficient ceiling cleaning device is provided which is arranged for longitudinal movement in the space between the ceiling section and the floor section and which does not require additional devices on the ceiling section, such as suction devices and the like. This does not only reduce the complexity of the construction of the coating booth, but also allows a reduction of the building height of the coating booth.
The ceiling cleaning device may include one or more suction hoses which are preferably controllably connected to a secondary filter of a powder recovery device, in particular with control provided by flaps.
The ceiling cleaning device provided according to the previous alternative embodiment of the coating booth is preferably arranged in the space between the ceiling section and the end position of the floor section. The ceiling cleaning device can move in a longitudinal direction, preferably using a telescopic rail, and can therefore be moved in this space in a manner so as to enable cleaning of the entire ceiling and floor section. The ceiling cleaning device blows air against the associated ceiling and floor regions through compressed air nozzles. The blown-off powder is immediately suctioned off via the suction device of the ceiling cleaning device and optionally transported to the secondary filter of a recovery device.
According to another embodiment, the ceiling cleaning device can include two cleaning units, which include compressed air nozzles and suction devices and which each clean only the associated half space between the ceiling section and the floor section. In all other aspects, the cleaning units can be designed so as to include all the detailed features of the ceiling cleaning device.
In summary, the invention provides a method for cleaning an interior space of a coating booth, wherein at least blast air is employed for removing the powder particles. In a primary cleaning operation with a complete color change, blast air is advantageously employed in combination with a corresponding suction, wherein blowing and suction can be carried out simultaneously, depending on the application. Blowing and/or suction can also optionally be performed cyclically several times, with the blast air preferably supplied intermittently or pulse-wise. Advantageously, the cleaning process can be accelerated by supplying blast air with an adjustable high-pressure.
In an inventive embodiment of a coating booth, in particular a powder coating booth, with a cleaning device, it is significant that the cleaning device forms simultaneously the floor section and/or the ceiling section of the booth during the coating operation, while for cleaning purposes being able to move in a vertical direction along the interior wall surface of the booth. Accordingly, the floor section and/or the ceiling section can simultaneously perform several functions, thereby eliminating the need for additional storage space outside the coating booth for a separate cleaning device. As a result, the coating booth can be compact and capable of automatically cleaning the interior space of the booth.